ORES OF THE SOUTH MOUNTAINS.
These mountains are a continuation of the Blue Ridge of Virginia, in the same geo logical formations and with the same ores; but here the Primal slates and sandstones, including the Potsdam, are repeated and undulated in folded axes. The range of the valley limestones through Maryland is limited to a narrow strip, but the same litho logical structure is maintained, and the same ores in the same geological position are found corresponding with those before described. We may here remark that the eastern range is not in the valley limestones, but rather on the Primal rocks bordering this side of the valley.
As before noticed, the eastern range of brown hematites frequently develops in large masses or deposits on the western flank of the Blue Ridge. The South Mountains are formed by an enlargement or spread of the Blue Ridge range, which bends to the west through the Cumberland and Lebanon ValleyS, forming a crescent, with its horns at Harper's Ferry and Reading, and its radius at the South Mountains.
The South Mountain "ore-banks" are about the centre or most western point of the bend, and among the ridges or Silurian hills which flank the western sides of the Azoic mountains. On the opposite or eastern flank are the magnetic ranges before described, but here concealed by the Mesozoic sandstones, which are pierced by the trappean rocks peculiar to the Azoic, which the Mesozoic conceals.
The ore is, we believe, entirely brown hematite, but diversified by the varieties which always exist in those mountain masses,—such as the compact, crystalline, porous, honeycomb, ochreous, and manganite,—forming of themselves a good mixture for reduction in the blast-furnace.
Manganese is generally found accompanying the brown oxides of this eastern range, as it sometimes is in that of the west and in the isolated deposits of the valley; but it is seldom intimately mixed with the ore. Certain layers, however, contain appreciable quantities, and the ore can be used in the furnace with or without it. When used in the shape of manganite, from 5 to 10 per cent. can be mixed with the burden of the furnace to great advantage in the reduction and improvement in the quality of the iron produced.
When very soft pig-iron is required, the manganite is not used; when hard iron is required, it is used in large quantities; but when strong, fibrous iron is desired, a moderate quantity can be used to great advantage.
It is not generally known that a judicious mixture of this ore with a variety of the brown hematites not only saves flux, but operates with much economy in the reduction of fuel. We have tried numerous practical experiments in this respect, and found that almost any quality-of iron nvight.be produced by those mixtures, and that a reduction of one-third the quantity of coal was not only possible, but eminently practical.
The value of our magnetic ores depends t-n their fusibility, or their purity and yield.
They, however, generally contain a small amount of manganese when found in the vicinity of limestone, as in some parts of the Sterling Mountain of New York. In such cases they are more calcareous than silicious, and are reduced with a less amount of fuel than when highly silicious and refractory.
A charcoal-furnace and bloomery has long been in operation at Mt. Holly, and are supplied with ores from the South Mountain ore-bank. The iron produced has always been celebrated for its strength and tenacity, particularly when in the shape of bar iron, and the blooms produced from the ore direct command an advance above the general market price.
These ore-beds, or banks, have recently been purchased by the South Mountain Iron Company, of which Hon. Henry D. Moore, of Philadelphia, is President. The estate embraces 20,000 acres of ore, timber, limestone, and farming-land. The ore-banks are about 14 miles southward from Carlisle, on the Cumberland Valley Railroad. Arrange ments are now being made to connect the mines, or banks, with this line, which will put them in direct communication with the anthracite furnaces of the Susquehanna, thus providing a source of supply much demanded by these furnaces, and a large and growing market for the production of the mines.
An analysis of the South Mountain ore, made by Du Bois & Williams, of Philadelphia, will be found below. It gives a high percentage for this class of ores, and compares favorably with the general yield of the Lake Superior or Cornwall ores. Forty-five per cent. is above the average yield of our brown hematites ; but we have reason to think that the ores of the South Mountain will exceed that amount, and when selected will yield fifty per cent. in the furnace.